<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8" />
  <meta http-equiv="X-UA-Compatible" content="IE=edge" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>选项卡</title>
  <style>
    * {
      margin: 0;
      padding: 0;
    }

    ul,
    ol,
    li {
      list-style: none;
    }

    .box {
      width: 600px;
      height: 400px;
      border: 3px solid pink;
      margin: 50px auto;
      display: flex;
      flex-direction: column;
    }

    .box>ul {
      height: 60px;
      display: flex;
    }

    .box>ul>li {
      flex: 1;
      background-color: skyblue;
      color: #fff;
      font-size: 20px;
      display: flex;
      justify-content: center;
      align-items: center;
      cursor: pointer;
    }

    .box>ul>li.active {
      background-color: orange;
    }

    .box>ol {
      flex: 1;
      position: relative;
    }

    .box>ol>li {
      width: 100%;
      height: 100%;
      background-color: pink;
      position: absolute;
      left: 0;
      top: 0;
      font-size: 100px;

      display: none;
    }

    .box>ol>li.active {
      display: block;
    }
  </style>
</head>

<body>
  <div class="box">
    <ul>
      <li class="active">a</li>
      <li>b</li>
      <li>c</li>
      <li>d</li>
    </ul>
    <ol>
      <li class="active">1</li>
      <li>2</li>
      <li>3</li>
      <li>4</li>
    </ol>
  </div>
  <script>
    var ul = document.querySelector('ul');
    var ol = document.querySelector('ol');
    var ulis = document.querySelectorAll('ul>li');
    var olis = document.querySelectorAll('ol>li');



    for (var i = 0; i < ulis.length; i++) {

      var btn = ulis[i];
      btn.index = i;


      btn.onclick = function () {

        for (var j = 0; j < ulis.length; j++) {
          ulis[j].className = '';
          olis[j].className = '';

        }

        ulis[this.index].classList.add('active');


        olis[this.index].className = "active";

      }


    }


  </script>
</body>

</html>